1. Field of the Invention
The present invention relates to a method of heating a composition provided over a substrate. The present invention further relates to a method of forming a glass pattern.
2. Description of the Related Art
A technique in which a highly airtight sealed structure is formed in such a manner that two substrates are bonded to each other by a glass layer including low-melting glass is known. In a technique disclosed in Patent Document 1, a sealed structure with high hermeticity is formed as follows: a paste containing a binder and glass fits (denoted by a “frit material” in the document) including low-melting glass is applied to a glass substrate along an edge of the glass substrate; by baking of the paste, the binder is removed and the glass fits are melted to form a glass layer (denoted by “frit glass” in the document); and the glass layer is irradiated with a laser beam with the substrate overlapping with a counter substrate, so that the glass layer is welded to the substrate and the counter substrate.
Since such a glass layer has a high gas barrier property, a sealed space can be kept away from the external atmosphere. A method of sealing using such a glass layer is applied to a device employing an element, such as an organic EL (electroluminescent) element, whose performance is rapidly impaired once the element is exposed to air (including moisture or oxygen).
Examples of the device employing an organic EL element are a lighting device using an organic EL element as a light source, an image display device in which a thin film transistor and an organic EL element are combined, and the like. An organic EL element can be formed into a film and can easily form a large-area element, which leads to a lighting device including a planar light source. In addition, an image display device using an organic EL element needs no, backlight which is necessary for a liquid crystal display device and the like, and accordingly, can achieve a thin, lightweight, high contrast, and low power consumption display device.